Thursday 26 September 2024
The End of Everything
Speaker: Steve Barrett
The guest speaker at the September u3a Todmorden members meeting was Steve Barrett, a Senior Research Fellow in the Department of Physics at the University of Liverpool. His subject was 'The End of Everything'.
For over an hour, Steve told us about what has been predicted to happen in the future. His first message was that although it took only three minutes to make our universe, it will take more than a trillion, trillion years for it to end.
The three minutes mentioned were immediately after 'big bang'. It has been calculated that, just before the big bang, every currently observable thing that is in our universe would have fitted into something the size of a golf ball. It has taken approximately 13.8 billion years for the universe to be as it is today. Steve's presentation assumes that the human race will deal with global warming, and avoids a third world war.
To try and help us get our heads round this, Steve's slideshow had a timeline, progressing from zero to eighty four horizontally. Each step was ten times further into the future, in years, than the one before. His example was a million years being three steps along from a thousand years, then another three steps to a billion years. Steve referred to these mind-boggling numbers as 'ten to the power of'…whatever step or number of years the event happened.
Planet Earth rotates on an axis around the sun, which currently 'points' us towards the North Star. But in ten thousand years, the earth's axis will have changed and it will be pointing in a different direction – to the very bright star known as Vega. The change for planet Earth at this time will be that it will bring it closer to the sun, which will affect the seasons we currently have, and is known as the 'Milankovitch Cycle'
Steve brought us forward to one hundred thousand years, ten to the five, on the timeline. Around this time the Voyager interplanetary exploration probes launched in the nineteen seventies will be leaving our universe. We know where the two probes are, and where they are going - to two separate solar systems. It's also predicted that at, or around, this time there will be another ice age.
We, as in scientists and other experts, know that the rotation of the earth is slowing down. Fairly recently, leap seconds have been added to various clocks and other timekeeping systems to ensure that the length of time is in sync with the rotation of the earth. The thinking is that, again in or around year 'ten to the five', a leap second will have to be added every day to maintain the speed of the rotation – compared with the thirty adjustments made over the last half century.
Some of the stars in our solar system will, as Stephen put it, 'go supernova'. This is a term for when they begin to collapse and release a large amount of energy, similar to that of our sun.
If our planet still exists, there will be two suns in our sky for a time, as a star called Gliese 710 passes by earth and goes through something called the oort cloud, which surrounds today's sun. This will lead to trails of comets from the sun for the next hundreds, or thousands, of years.
Steve returned to some aspects of what would happen as time went by, mentioning Saturn's rings. One of the theories is that the planet's surface, over time, was damaged in some way and debris was pulverised and sent into space. It may subsequently have been drawn back to the planet, forming the rings that are visible today, but over time have been reduced by the effect of gravity – and will eventually disappear.
In or around the same time, ten to the power of eight, or a hundred million years from now there may be an 'Extinction Level Event'. He said that these events, leading to mass extinctions, would probably have been caused by asteroids, large rocks and other things hitting our planet – the last event being around 66 million years ago when dinosaurs became extinct.
As of now, planet Earth isn't near to any stars or planets that will turn into supernovas, but this could change over time, perhaps enough time for humans, if they are still around, to come up with ideas to avoid the next such event.
In the same time period, the distance from Earth to the Moon will increase. This means that the angular momentum, or spin, of the Earth will slow down. The length of a day will become 25 hours, leading to the seasons, spring, summer etc, altering in terms of time and effect. No more total eclipses as time progresses to ten to the power of nine, or a billion years, and the moon gets closer to the sun. In the same period, our sun will slowly increase in size and luminosity, as it moves towards its red giant phase. In the following periods of a billion years this will increase by ten percent each time.
This will lead to planet Earth having a surface temperature of eighty degrees centigrade, meaning all oceans would burn dry. Steve said that the only way that humans could survive might be to leave planet Earth. But some experts have suggested that Earth might survive, as the sun may lose its mass because of strong solar winds, along with less gravity pulling earth towards it.
Into period ten to the power of ten, or ten billion years, and the sun will become a white dwarf. This is when the sun has lost almost all its mass and magnetism. Earth, by this time, will be much further away from the sun, possibly where Mars is today. Our planet will also have lost its magnetic field and will be exposed to radiation and cosmic rays. Earth will still have a core of radioactive decay and other elements, but the core will eventually solidify, and our galaxy – the milky way - will merge with its neighbour, Andromeda. Earth will, again, become tidally locked to the moon.
Steve then guided us through the events occurring in even more unimaginable, even bewildering, time frames, the final one being ten to the power of eighty-four. Along the way, we heard that all galaxies will merge, moving beyond our horizon. After a trillion years, the universe will run out of hydrogen. Stars, which might form from gas, will eventually go out and drift through space.
Left: Example of a White Dwarf.
Right: Crater on the surface of Saturn – the cause of Saturn's rings?
White dwarves, such as the sun, will cool down, becoming black dwarves, and any stars not ejected from the galaxy will be 'eaten' by the SMBH – super massive black hole. The SMBH's themselves might merge with each other, but all of them will eventually evaporate, the last one by year Googol – ten to the power of one hundred.
After this happens….nothing.
Steve concluded with an epilogue. It took millions of years for the elements, events and conditions to take place for any kind of life as we know it. We live in an age when the sun is, as he said 'middle aged and well behaved' and the Moon keeps Earth on an even keel.
The audience showed their appreciation with well-deserved applause for his captivating presentation.
The next Todmorden U3A Monthly Members Meeting will be at 2pm on Thursday 17th October 2024, open to all fully paid-up members at the Todmorden Learning Centre and Community Hub (TLCCH), Todmorden. The speaker for this meeting is Norman Harris, who will take us on 'A journey from Atlantic to Pacific via the Panama Canal.
Not yet a member? We're always delighted to welcome new members. Contact details: website at www.u3atod.org.uk or email at info@u3atod.org.uk.
Many thanks to Colin Sanson for this report
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