Carl Sagan 1934 - 1996
Monday, 7 September 2026
Climate Change - UN Report 'Limiting the Overshoot' shows 1.5°C increase has been crossed
Sunday, 6 September 2026
Astronomy - Three giants of the universe - comprehending Black Holes
Three
remarkable examples are TON 618, M87* and Sagittarius A*. All
three are supermassive black holes, but they differ enormously in size,
distance and activity.
TON 618 — The Colossus
TON 618 is
among the most massive black holes known thus far and it lies at the heart of an
extraordinarily luminous quasar—a phenomenon produced when matter
falling towards a supermassive black hole releases enormous amounts of energy.
The black hole itself cannot be seen. Instead, the brilliant environment
surrounding it as material is drawn into the black hole's gravitational
influence is what can been viewed.
TON 618 — essential facts
- Category: Extremely massive supermassive black hole powering a quasar
- Estimated mass: Approximately 40 billion times the mass of the Sun
- Distance: Approximately 18.2 billion light-years in present-day
comoving distance
- Light-travel time: Approximately 10.8 billion years
- Estimated event-horizon diameter: Approximately 160 billion kilometres
- Equivalent scale: About 1,070 times the Earth–Sun distance
- Significance: One of the most massive black holes known
It's estimated event-horizon scale is itself difficult to comprehend. If placed at the centre of Earth's Solar System, it would extend far beyond the orbit of Pluto.
M87* — The Black Hole that has been imaged
At the
centre of the giant elliptical galaxy Messier 87 lies another
extraordinary supermassive black hole: M87*. M87* became famous in 2019 when
the Event Horizon Telescope collaboration produced the first image of a
black-hole shadow. The image showed the glowing material surrounding the black
hole and the dark region created by its extreme gravitational field. M87* is
also associated with a spectacular relativistic jet, extending thousands
of light-years into space.
- Category: Supermassive black hole at the centre of a giant elliptical galaxy
- Estimated mass: Approximately 6.5 billion times the mass of the Sun
- Distance: Approximately 55 million light-years
- Estimated event-horizon diameter: Approximately 38 billion kilometres
- Equivalent scale: About 257 astronomical units
- Special significance: First black hole to have its shadow directly imaged
- Additional feature: Powerful relativistic jet extending thousands of light-years
Sagittarius
A*, usually abbreviated to Sgr A* is the supermassive black hole at the centre
of the Milky Way, approximately 26,000 light-years from Earth. Compared with
TON 618 and M87*, Sagittarius A* is surprisingly small, yet four million solar
masses concentrated into such a compact region still produce an extraordinary
gravitational environment. Unlike TON 618, Sagittarius A* is currently
relatively quiescent. It is not behaving as a brilliant quasar, although gas,
dust and stars are constantly interacting with its powerful gravitational
field.
Sagittarius A* — essential facts
- Category: Supermassive black hole at the centre of the Milky Way
- Estimated mass: Approximately 4.3 million times the mass of the Sun
- Distance: Approximately 26,000 light-years
- Estimated event-horizon diameter: Approximately 25 million kilometres
- Equivalent scale: About 0.17 astronomical units
- Activity: Relatively quiescent compared with an active quasar
- Special significance: Close enough for astronomers to study individual stars orbiting around it
Sagittarius
A* is therefore the closest opportunity for Earth's astronomers to study a supermassive black hole in
detail.
Three Black Holes — One Extraordinary Phenomenon
The
differences between these three objects are staggering.
- Sagittarius A* contains approximately 4.3 million solar masses.
- M87* contains approximately 6.5 billion—more than 1,000 times the mass of Sagittarius A*.
- TON 618, with an estimated 40 billion solar masses, contains roughly 10,000
times the mass of Sagittarius A*.
All three belong to the same fundamental astronomical category: supermassive black holes. Sagittarius A* is the comparatively quiet giant residing at the centre of our own galaxy. M87* is a much larger black hole whose environment produces a spectacular relativistic jet—and whose shadow humanity has now imaged. TON 618 represents the extreme end of the scale: a colossal black hole powering one of the Universe's most luminous quasars.
These three objects offer three extraordinary perspectives on the same phenomenon. They are among the most extreme objects produced by nature—places where gravity becomes so powerful that space, time and light itself behave in ways that challenge the understanding of reality.
Climate Change - Geoengineering - solar radiation deflectors
As global heating heads to 1.8C, is it time to consider the ‘Voldemort’ of climate policy?
The world is set to miss the 1.5°C global warming target, and plans are underway for UN climate talks in the Pacific and Turkey.
Climate mitigation – reducing or preventing greenhouse emissions – was once treated as the only legitimate response to global warming. In comparison, climate adaptation – trying to adjust to global warming – was seen as a form of defeatism, or worse, hubris.
But that taboo has long since lifted: our collective failure to prevent climate change means adaptation is now an essential part of climate policy.
Similarly, attitudes to actively removing carbon dioxide from the atmosphere have undergone an evolution. While there are reasons to doubt whether carbon removal can work at scale, Australia’s “net zero emissions” plans rely on these interventions.
Now, the taboo surrounding another controversial form of climate intervention – solar radiation modification (SRM) – appears to be lifting.
What is solar radiation modification?
SRM refers to large-scale technological interventions that reflect a small amount of sunlight back into space, thereby lowering global temperatures. Increasingly called the more benign term “climate stabilisation”, the proposed methods include space mirrors – satellites equipped with large reflective surfaces – and cloud brightening, where microscopic particles are sprayed into clouds to make them more reflective.
The most commonly discussed SRM technique is stratospheric aerosol injection (SAI) – the release of particles into the upper atmosphere to recreate the cooling effects observed following volcanic eruptions.
SRM is so controversial it’s sometimes called the “Voldemort of climate policy”. While it could reduce global temperatures, it does not limit carbon emissions, and the ecological effects of deployment are uncertain.
Some critics are worried a potential techno-fix will deter mitigation efforts. Others point out the risks of “termination shock”: once implemented, ending SRM would cause abrupt temperature rise. Scientific research suggests the strong warming experienced since 2023 is likely a case of inadvertent termination shock. When new fuel regulations reduced sulphur dioxide emissions from international shipping, the rapid warming that followed revealed this pollution had, incidentally, been cooling the planet.
At present, SRM inhabits an international and domestic policy vacuum. Many scholars advocate for a ban on both research and deployment, saying these technologies “play God” with nature. We argue a ban on research is no longer tenable.
Why challenge the taboo?
The case for taking SRM seriously does not usually rest on enthusiasm for the technologies, but on global warming’s grim reality. We are approaching planetary tipping points such as significant polar sea ice retreat, the death of the Amazon rainforest and widespread coral reef loss. SRM advocates say it should be viewed as a complement, not an alternative, to mitigation: a means of limiting the extent and duration of temperature overshoot while decarbonisation continues.
Government appetite for this approach is limited and patchy. When the UN Environment Assembly discussed a Swiss proposal for SRM research in 2024, countries could not agree even on whether and how to regulate research in this area. Countries such as Japan and Saudi Arabia pushed for ongoing research, while vulnerable Pacific and African countries argued against any language that risked endorsing the practice.
Nowhere is the politics of SRM more volatile than the United States. One group of Republicans reject the climate change “hoax” but is so convinced SRM is already happening that many Republican states have criminalised it. Some think tanks advocate SRM as a way to defend “American Weather Sovereignty”. NASA has an exploratory program investigating space-based reflective dust clouds. For now, the Trump administration has not chosen a side, but it’s easy to imagine a future administration unilaterally blocking, or implementing, SRM.
If we don’t challenge the SRM taboo, self-interested actors are poised to fill the policy vacuum. Elon Musk has recently spoken out in favour of SRM, while ventures such as the US-Israeli startup Stardust are pursuing research without public oversight.
What is Australia’s position?
Australia has no policy on SRM research or deployment, but federal government funds have supported related research into local interventions, including the Reef Restoration and Adaptation Program (RRAP). This trialled the world’s most respected marine cloud brightening research over the Great Barrier Reef.
Existing environmental and climate law might regulate risks posed by small-scale research, but does not consider the larger risks of eventual deployment. With the exception of some ad hoc efforts, SRM research is not subject to any dedicated ethics framework.
The planetary scale of SRM impacts means we urgently need research to consider the geographic distribution of benefits and harms from any deployment, and the security implications of unilateral deployment by any state or private actor.
What should Australia do?
As a trusted middle power, Australia is well positioned to help lead discussions on the future of SRM. At a minimum, Australia should assess the potential impacts of various options on Australia’s climate, agricultural production and natural environment, and develop a public position on research.
Waiting until a foreign government or well-resourced private actor forces the issue would leave Australia reacting to decisions made elsewhere. Instead, we should prepare for the surprises a fast-moving, under-governed field is likely to produce.
As temperature overshoot becomes an inevitability, SRM is emerging as a new element of international climate policy whether we like it or not. We do not argue anyone should deploy SRM, but that we should break the taboo and enable responsible scientific research and public deliberation.![]()
Jan McDonald, Professor of Environmental Law, University of Tasmania; Jonathan Symons, Director of Research and Innovation, School of International Studies, Macquarie University; Manon Simon, Researcher in Climate Intervention Law and Governance, University of Tasmania; Matt McDonald, Professor of International Relations, The University of Queensland, and Rachel Neef, Research fellow, Faculty of Law, University of Tasmania
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Climate Change - a monster El Niño event for the world in 2026
A record‑shattering El Niño is almost here. Here’s what that means for the world’s weather
The world is bracing for the strongest El Niño in history.
The United Nations has made the grim prediction that our planet now sits in the “danger zone” of extreme weather. That’s based on data suggesting the current El Niño will break all previous records.
El Niño is a naturally occurring weather phenomenon that drives variations in temperature and winds across the Pacific Ocean and influences weather around the globe.
Globally, we have endured many strong El Niños in the past, but none have been as exceptionally strong and developed as quick as this one.
So what’s behind this potentially record-breaking El Niño? And how might it affect weather across the globe?
An exceptional El Niño
Scientists track El Niño activity using temperature data from the tropical Pacific Ocean near the equator. Historically, this involved measuring how high or low temperatures were across this region.
However, scientists and weather organisations – including Australia’s Bureau of Meteorology – now use a relative index. Instead of simply measuring temperatures, this relative index accounts for any background warming due to climate change. This makes it much easier for scientists to identify how intense an El Niño is in a warming climate.
The current El Niño stands out for two main reasons.
Extra early
El Niño typically peaks in the period between November and January, but this one is already unusually warm this early in the season and is yet to peak during summer.
Extra hot
Recent data shows the relative index for August were 2.3°C above average, stronger compared to other El Niño years. In Australia, El Niño years tend to coincide with hotter and drier conditions. However, every El Niño is different and can lead to different impacts. However, this El Niño will lead to record breaking global temperatures in 2027.
How is it affecting the world’s weather?
This historic El Niño is already altering weather around the globe.
We see its most direct and severe impacts in countries surrounding the Pacific Ocean. Indonesia, for example, just this month was battling massive wildfires. Scientists understand the current El Nino is a major driver of these increasingly fierce blazes.
El Niño is also reshaping how and where cyclones form. Satellite pictures reveal there are currently four active tropical cyclones in the Pacific, from near Japan to as far away as Hawaii. This is extremely unusual. El Niño typically boosts cyclone activity in the eastern and central Pacific by carrying warmer water to those regions. Usually we only see one or two such cyclones.
In Australia, we are slightly more removed from the effects of El Niño. However, we can expect to feel its presence more strongly as we head into spring.
The Bureau of Meteorology’s seasonal forecast suggests Australia has so far had a textbook response to El Niño. Temperatures are rising – up to an unseasonable 37°C this week in parts of northern Australia – and conditions are getting drier. Much of eastern and central Australia can expect an unusually dry spring and summer, potentially heightening bushfire risk.
However, a record-breaking El Niño will not necesssarily trigger catastrophic bushfires in Australia. Consider three of the last strong El Niño we’ve experienced. In 1982, a robust El Niño coincided with drought-like conditions. In contrast, during the El Niño years of 1997–98 and 2015–16, some parts of Australia received drenching rain while other regions barely registered any moisture.
What may lie ahead
The intensifying El Niño will likely exacerbate the consequences of climate change.
As El Niño strengthens, countries around the world will be forced to grapple with increasingly extreme weather. Tragically, the most disadvantaged will be the hardest hit, with nearly 50 million people in vulnerable communities likely to be pushed into acute hunger. Farmers across the globe face more unpredictable weather, from crop-destroying floods in South America to severe drought in parts of Africa.
To protect the world’s people and ecosystems, governments must invest in robust research. We urgently need more modelling capability to identify which regions will be worst affected by the strengthening El Niño. This is particularly true for Australia, where a lack of understanding of how climate change on top of a strong El Niño will affect local conditions.
This record-shattering El Niño is already compounding the destructive effects of climate change. But it may be just the catalyst we need to finally abandon fossil fuels and curb our world-warming emissions.![]()
Mandy Freund, Lecturer, Climate Science Geography, The University of Melbourne
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Wednesday, 2 September 2026
Artificial Intelligence - 12 most widely used AI systems in 2026
- ChatGPT (OpenAI): approx 1 billion active weekly users and the largest standalone AI assistant at present.
- Llama 4 (Meta AI): 1.2 billion monthly active users across Meta's apps. Mostly this AI is embedded in WhatsApp/Instagram/Messenger rather than as a standalone chat model.
- Gemini (Google): around 950 million active monthly users on the standalone app. Separately, Gemini powered AI overviews reach over 2 billion monthly users through integration with Google Search.
- Microsoft Copilot: (GPT based + Microsoft) around 420 million monthly active users across all operating systems. This is expanding to Copilot being bundled with Microsoft 365 and operating systems.
- DonBao (Byte Dance): approx 260 million monthly active users. This is an increase of 300% from 2025. This is China's top consumer AI app.
- Ernie Bot (Baidu): Monthly active users has passed 200 million however it is tied to Baidu Search.
- DeepSeek (Deepseek): around 130 million users at the end of 2025. Majority of users are located in China although the AI model has a broad global fooprint.
- Qwen (Alibaba): This AI model has now exceeded 100 million active monthly users and has a strong presence in China and in the open-weight AI community.
- Claude (Anthropic): estimates on users vary widely depending on the source and method of estimation. The range is between 70 and 250 million users per month. This is the fastest growing Western AI assistant with a year-on-year growth of a staggering 855%.
- Perplexity: approx 45 million monthly active users. This model is predominantly an AI first search and answer engine rather than an LLM chat system.
- Grok (xAI): No reliable standalone figure as this AI model is often connected via X's social media platform which has hundreds of millions of users. Grok can be used as a standalone model without using X.
- Kimi (Moonshot AI): a more recent AI model launched this year and still gaining traction. A Chinese AI app it is significantly smaller than the other AI models and its number of users is only in the tens of millions in China.
Tuesday, 1 September 2026
Environment - Climate change - large companies see a hotter world as the reality
Some of Australia’s biggest companies are planning for an unbearable climate future
Even as unprecedented fires and heatwaves rage across Europe, scientists track the retreat of Antarctic sea ice and a supercharged El Niño system heads our way, Australia’s largest companies are forecasting business-as-usual in a much hotter world.
Last year, Australia introduced mandatory company climate reporting. They must now disclose the climate “risks and opportunities” that may affect their prospects.
Several of Australia’s biggest energy and resource companies have now published new sustainability reports as part of annual financial reporting.
Their disclosures reveal the climate future they are planning for, and whether this is aligned with international science-based targets such as the Paris Agreement’s 1.5°C warming threshold.
What we’re seeing is alarming.
Companies planning for an unbearable future
Most of these reports indicate big companies are developing strategies on a climate change “base case” – a representation of what they consider most likely to happen – of more than 2°C of warming. The future temperature rise they’re planning for is one scientists say would deliver an unbearably hot planet.
Some of Australia’s largest miners have followed this approach. Both Rio Tinto and BHP expect global temperature increases of more than 2°C by the end of the century.
Not every company reveals the increase in global temperature they are planning for. But even if they don’t, their disclosures show they’re not expecting temperatures to hold to 1.5°C.
Energy companies AGL and Origin Energy both express confidence their strategies and business models will remain robust, even if temperatures accelerate beyond 2.6°C warming. This increase would put the Australian economy, environment and community at severe risk.
Companies hold power
Companies often argue that governments are responsible for creating policy to address global warming. But this underestimates the power corporate leaders hold to shape Australia’s shared climate future through financial decisions.
For example, mining giant BHP expects demand for steelmaking coal to remain robust for decades, with customers from China, India and Southeast Asia. This underpins the valuation of its major export commodities, and appears to justify the lack of plans to scale down steelmaking coal production. However, this assumption sits uneasily with the fact these same countries have their own net-zero targets.
Similarly, Rio Tinto confirms “no portfolio adjustments” are made to its future production plans. Its central case estimate of 2.1–2.3°C of warming by 2100 assumes developing countries will miss or delay their stated net-zero targets, underwriting business-as-usual production for the company.
Disclosures out of step with science
However, the assumption that business-as-usual will be possible in a hotter world is out of step with the latest science. The Paris Agreement’s temperature goal was set in 2015 based on exhaustive scientific assessments that warming of more than 2°C would be dangerous, and limiting warming to 1.5°C was necessary to minimise climate risks.
Scientific knowledge about how much global warming is “safe” has exponentially increased. It reemphasises the need to keep to 1.5°C with “limited overshoot”. This means we can only exceed 1.5°C temporarily, and simultaneously need to be working to bring temperatures back down. Only then will we minimise irreversible changes such as sea level rise, the disappearance of coral reefs or vast sea ice loss at the poles.
Scientific best estimates find we can’t go over 1.5°C by more than 0.1–0.3°C (a “peak temperature” of 1.6–1.8°C) and still return warming to safe levels. Even then, the longer we stay above 1.5°C and the extent to which we exceed this threshold, the more devastating the outcome.
Is this legal?
Legally, there’s no issue with companies using a base case for planning that exceeds 2°C of warming. But this approach isn’t in line with Australia’s broader international legal obligations. Companies will likely face increased investor scrutiny or reputational blowback when they walk back climate commitments.
In July 2025, the world’s highest court, the International Court of Justice (ICJ), confirmed 1.5°C is the temperature limit countries are aiming for. To meet their Paris Agreement promises, governments — including Australia — have to show the most ambitious action the country can realistically take to help keep warming under 1.5°C. Australia’s latest plan for a 62–70% emissions cut from 2005 levels was submitted in September 2025.
The court confirmed the Paris Agreement also requires governments to take action at home to cut emissions in line with the 1.5°C goal — including introducing rules for businesses operating in their countries. To follow international law, the Australian government needs to use every tool available to regulate the emissions of big companies, based on the best available science. Countries that don’t comply could be sued before the ICJ and ordered to pay compensation to other nations.
What about Australia’s climate policy?
Big companies in Australia contribute more than 30% of our domestic emissions. If we also include emissions from the fossil fuels some of these companies produce, it raises Australia’s global carbon footprint to around 4.5% of global fossil carbon dioxide emissions, second only to Russia. Making sure big companies do their bit to reduce emissions is essential for Australia to meet its climate targets.
This year, Australia is the “President of Negotiations” for COP31. This is an opportunity for Australia to show it’s doing all it can – internationally and in its own backyard – to support compliance with the Paris Agreement and accelerate climate action. From their new disclosures, it doesn’t seem that Australia’s biggest companies have got the memo.![]()
Jacqueline Peel, Professor of Law, The University of Melbourne; Nina Araneta-Alana, Research fellow, Laureate Program on Global Corporate Climate Accountability, The University of Melbourne, and Suzanne Varrall, Research Fellow, Laureate Program on Global Corporate Climate Accountability, The University of Melbourne
This article is republished from The Conversation under a Creative Commons license. Read the original article.
International Relations - the threat of old military munitions
Landmines and remnants of war pose a serious threat, and more needs to be done to solve it
In recent weeks, wildfires have ravaged Europe amid record-breaking heat and drought. These fires posed an immediate threat to life, forcing the evacuation of over 300,000 people across France, Spain and Portugal. Rivers across Europe have also hit record low water levels.
These developments have highlighted a deadly legacy of past conflict: unexploded bombs and other munitions.
Fires in southern France exposed a previously unidentified cache of 400 French and German shells from the second world war. The ammunition detonated in the heat of the fire, forcing authorities to clear the area before residents could return.
Dropping water levels have also revealed unexploded munitions in the Netherlands, Hungary, and Slovakia.
But fires and drought in Europe are only the latest reminder of an enduring problem that affects millions worldwide.
Explosive remnants of war
Since the first world war, numerous conflicts have ravaged the world, scarring the landscape and littering battlefields with unexploded, abandoned, or otherwise discarded munitions.
Known as explosive remnants of war (ERW), unexploded munitions posed a continuing threat to an estimated 100 million people across 60 countries in 2025.
ERW includes two categories of ordnance. The first is unexploded ordnance (UXO), which are explosive weapons that failed to detonate when they were first deployed. The second is abandoned explosive ordnance (AXO), left behind after a conflict.
The bomb located in Budapest would be classed as an unexploded ordnance, but the cache that detonated amid the Gironde fires appears to fall into the latter category.
Both can include a variety of different munition types, from artillery shells and mortars to grenades and large bombs dropped from aircraft.
Beyond these, landmines are another key explosive contaminant. Landmines are not legally classed as explosive remnants of war because they are deliberately placed during conflict. Yet their extensive use in conflicts globally makes them one of the key explosive contaminants of conflict.
What countries are affected?
After the second world war, European countries worked quickly to remove the landmines that had been put in place during the conflict. In the Netherlands alone, almost 1.4 million mines were cleared between May and November 1945. A similar number were laid by German forces in Denmark, which cleared most of its known minefields by the end of 1945.
As of 2024, the United Kingdom, France, Germany and Denmark are all classed as having completed mine clearance.
Yet globally at least 57 states and other areas remain contaminated by antipersonnel landmines as of October 2025. Many of these are in Africa, the Middle East and Asia.
Among the countries most contaminated by landmines are Afghanistan, Bosnia and Herzegovina, Cambodia, Ethiopia, Iraq, Türkiye, Ukraine, and Western Sahara.
Some were laid during the second world war. This includes minefields placed by both Allied and Axis forces across Algeria, Egypt, Libya, Morocco and Tunisia as part of the North Africa campaign.
Subsequent conflicts also led to extensive minefields being laid. For example, the Vietnam War left nearly 20% of the country contaminated by landmines — an area the size of Tasmania. Decades of conflict left neighbouring Cambodia heavily contaminated, while the Iran-Iraq War left millions of unmarked mines littering the border regions.
Identifying the exact number of countries contaminated by remnants of war is more difficult, with any place that has seen conflict potentially affected. While a country can be deemed free of landmine contamination, it may still be faced with the risk of remnants of war.
In the first world war alone, more than 700 million shells and mortar bombs were fired across the Western Front. An estimated 140 million of these failed to detonate. Each year, Belgian and French farmers routinely collect these and other UXO as part of what is known as the Iron Harvest.
Closer to home, remnants of war from the second world war continue to kill and maim those who encounter them. This includes an Australian killed while handling a mortar shell in the Solomon Islands, with several UXO also located across Darwin in recent years.
Broader implications
According to the Land Mine Monitor, more than 6,000 people were killed or injured by landmines and remnants of war in 2024. Most of these casualties were civilians, with reported casualties spanning no fewer than 52 countries.
The primary danger relates to the detonation of landmines and remnants of war, but the threat they pose goes beyond safety and physical harm.
Studies have shown their presence can restrict access to arable lands, impact soil and water quality, affect food security and diversity, and stunt economic development.
These risks are exacerbated by increasingly frequent and extreme weather and natural disasters driven by climate change. Flood events can relocate and unearth landmines and other remnants, while wildfires can detonate them unexpectedly.
Meanwhile, dropping water levels in rivers and lakes can expose civilians to greater risk of harm by allowing access to contaminated riverbeds that would otherwise be inaccessible.
This is also not a historical issue. Anti-personnel mines are still being used in conflicts such as the war in Ukraine, and several European nations have withdrawn from a treaty designed to prohibit their use.
Military-led operations are working to clear remnants of war in many places, including Pacific island countries. However, these recent events are a reminder of the ongoing threat of remnants of war and landmines, and the need for an integrated approach that recognises and responds to the broader risks and challenges they pose.![]()
Nicole Townsend, Lecturer in War Studies, UNSW
This article is republished from The Conversation under a Creative Commons license. Read the original article.


