Close-up reveals tiny ‘campfires’ on the Sun
How do we know the Sun will rise tomorrow? Thanks to stunning new satellite images, we know more about the Sun than ever. But we are still no closer to solving the deepest problem of all.
Every morning, something miraculous happens.
A 4.6-billion-year-old sphere of burning, hot plasma – one million times the size of the Earth – rises into the sky. Although the Sun is a staggering 152 million kilometres away, we can feel its heat on our skin as it turns night to day and keeps life on Earth humming along.
Now, a space probe has sent back incredible pictures of tiny flares in its outer atmosphere. These so-called “campfires” are a millionth the size of those visible from Earth. Delighted by the discovery, astronomers hope the images will help solve some of the mysteries of our nearest star.
Our burning obsession with the Sun goes back thousands of years. Ancient civilisations worshipped it as a deity, to be feared and obeyed. It was associated with the power of the Egyptian pharaohs, and Hindus continue to pray at dawn to Surya, the Sun god who rides a horse-drawn chariot across the sky.
As the source of life-preserving light, keeping the Sun happy has always been important. We may find strange the rituals of Aztec human sacrifice or the Sun Dance of the Lakota. But religious ceremonies are how many people throughout history have dealt with the fear that the Sun might not always be with us.
A vanishing Sun may sound far-fetched, especially on a summer’s day in the middle of a climate crisis.
But for millennia, solar eclipses and other optical phenomena have been interpreted as omens and portents. At other times, volcanic eruptions have blotted out the Sun, causing years without summers, and inspired apocalyptic myths of the end of the world.
So, unsurprisingly, predicting the Sun’s movements has always been a serious business. Over 4,000 years ago, a Chinese emperor is reported to have beheaded two astronomers for failing to foresee an eclipse. Christopher Columbus had more luck in 1504, when he used a lunar eclipse to escape starvation. Since Columbus, huge advances in physics and the power of telescopes have vastly increased our knowledge of the Sun and the heavens.
And, thanks to 20th-Century astrophysics, we can now calculate that our star has enough hydrogen fuel to burn for another five billion years. That’s 1.8 trillion sunrises to look forward to. An incredible feat of prediction and a resounding victory of science over superstition, and knowledge over ignorance.
Not so fast. The 18th-Century philosopher David Hume warned that predictions are based on the assumption that the future will resemble the past. What has always happened will continue to happen.
It’s a fair assumption, but that’s all it is. Our ancestors believed angry gods controlled the weather; we believe there are unchangeable laws of nature. But the future may have other ideas.
Hume’s problem of induction has troubled philosophers ever since. His scepticism is why scientists talk about probabilities, not certainties. It may not stop you from sleeping tonight, but it should give you pause for thought.
So, do we know the Sun will rise tomorrow?
Yes, say some, we do. The philosophers are splitting hairs. We have sent probes out into the solar system and built powerful telescopes to monitor the movements of the stars and planets. We understand the Sun far better than our superstitious ancestors, and rely on much more than past experience or blind faith.
No, say others, we don’t. History is full of improbable and unlikely events, and belief systems that have come crashing down without warning. You can no more prove that the future will be like the past than the Sun worshipper can prove their rituals please the Sun god. We all will just have to wait and see.
- Is uncertainty scary or exciting?
- Is there anything we can be certain will happen in the future?
- Create your own myth to explain why the Sun rises, and draw a comic strip to explain it.
- Write a science-fiction short story that begins: “Today, the Sun did not rise.”
Some People Say...
“What has been will be again, what has been done will be done again; there is nothing new under the Sun.”The Bible, Ecclesiastes 1:9
What do you think?
Q & A
- What do we know?
- Most agree that the past is a good measure of the future. The Sun has risen every day for the last 1.7 trillion days, and it is reasonable to assume it will continue to do so. However, Hume wanted us to treat this idea critically and leave open the possibility that we might be wrong. After Hume, science and philosophy were influenced by the ideas of Karl Popper. He argued that a theory is true until proved wrong. So, for now at least, science agrees that the Sun will rise tomorrow.
- What do we not know?
- One main area of debate is around how serious this philosophical problem really is. Hume was writing before modern advances in probability and statistics. His contemporaries talked about natural laws and certainties, but modern scientists prefer to say future events are highly probable. For most of us, this is good enough. However, some thinkers, like the statistician Nassim Nicholas Taleb, argue that the highly improbable happens all the time.
- Space probe
- The Solar Orbiter completed its first pass of the Sun last month, taking the closest-ever images. One physicist working on the mission described it as “much better than we dared to hope for”.
- The next step will be to measure the temperature of these fires to help understand why the corona (outer atmosphere) is 300 times hotter than the Sun’s surface.
- Sun Dance
- The ritual of the North American Plains cultures involves extreme endurance, fasting, and ceremonial piercing. The full details of the ceremony remain a proudly guarded secret of the indigenous people.
- Optical phenomena
- Unexpected solar events have changed the course of history. In 1461, a rare “Sun dog”, the illusion of three suns rising, inspired the young Edward IV to victory in the Wars of the Roses.
- A sign or warning that a momentous or disastrous event is likely to happen.
- Years without summers
- The 1815 eruption of Mount Tambora in modern-day Indonesia caused temperatures to plummet around the world, leading to crop failures and famine.
- End of the world
- Ragnarök in Norse mythology is the catastrophic battle that will end the world. In the chaos, a wolf god chasing the Sun across the sky will finally catch the Sun and devour it.
- Christopher Columbus
- In 1504, Columbus was marooned on the island of Jamaica. When the indigenous population refused to supply his crew with food, he used an astronomical book to intimidate the natives of the island, successfully predicted a total lunar eclipse.
- In January, the most powerful solar telescope in history began to take images of the Sun. The Daniel K Inouye Solar Telescope in Hawaii is four metres wide, took two decades to build, and is studying the star in extraordinary detail.
- David Hume
- The Scottish Enlightenment philosopher (1711-1776) argued that all human knowledge is acquired from experience.
- Problem of induction
- We use inductive reasoning whenever we use our memory of past experiences to help predict what will happen when we encounter something new. But this relies on the “rules of nature” staying the same, and the only evidence we have for this is from experience. A circular argument and a big headache for anyone trying to predict the future.
- Splitting hairs
- Arguing about very trivial differences or unimportant details.