Q & A

Do you think that, because our earth is warming up and changing because of that, it will have an effect on the whole universe, or are we too small to create a universal problem?

Corian Huigen - Netherlands

We are indeed VERY small, Corian .... on the scale of the Universe, on the scale even of our Galaxy, and even on the scale of our tiny solar System. It is certain that if the earth were to be unexpectedly fried tomorrow, physically there would be very little effect felt in the rest of the Universe . Whether or not the spiritual effect would be on a different scale is impossible for me to answer.

Cheers

Brian May

If the universe were to stop expanding, would it eventually fill with mass (stars, planets, and such) or does it have a set amount of mass? And since the universe is continuing to expand, shouldn't the book BANG! be getting larger as well?

Nikki Pace - Nebraska, USA

Hi Nikki

We believe that the Universe today contains a set amount of mass, and that no more is being created. In fact, stars are essentially large nuclear reactors, converting matter into energy, and so the total amount of matter in the Universe must be decreasing slightly; the Sun loses four million
tonnes of matter every second.

As for your other point, on 'small' scales other forces dominate over the Universe's expansion. In the case of the book, it's the bonds between the atoms and molecules that make up our carefully crafted text, while on the scale of our local group of galaxies gravity is strong enough for now to keep the group intact. That's why we're approaching the Andromeda galaxy rather than seeing it recede with more distant systems. Things may be different in the future - but you'll have to read the last chapter of Bang! for that story...

Chris Lintott

What is it that actually warrants something qualifying a planet then if Pluto had been removed?

Danielle Friel - Birmingham, UK

I have to you to say I find myself quite indifferent to this whole discussion on what qualifies as a planet!!! But that's just me ... I'm more interested in what is inside Pluto than what it is classified as! But astronomers worldwide are still arguing about this. Currently one of the qualifications you need for being a planet is that you have to have swept up all the local debris, and created an empty zone in the neighbourhood of your orbit! But I feel sure this will change as the discussion continues. I refer you to Sir Patrick ... he gave a great up-to-date explanation in the recent edition of the Sky at Night magazine.

Brian May

When will the universe stop existing?

Dagmara - Warsaw, Poland

Well, Dagmara, thanks for my first question - and I'm glad you are enjoying the site.

When will the Universe cease to exist? Well, to all intents and purposes, I think the answer is 'never'. You will see, at the end of BANG!, a section where we look at possible final states of the Universe. The point where we think all the stars will have run out of fuel to make them shine is at about 10¹³ years from now. This number is quite quick and easy to say, but represents an unimaginably long time - about ten thousand times as long as the Universe has already been in existence - which as we have seen is reckoned to be more than thirteen billion years. If this distantly future universe, a bleak, scattered population of black holes, dead stars, and the remains of planets, continues to expand, as at present most cosmologists think it will, then there is still no real 'end' in sight. Locally the gravitational pull of black holes may continue to absorb some of the scattered debris, but even the black holes do not seem to be the end of the line, since "Hawking Radiation" given enough time, seems to give a mechanism for the ultimate dispersal of black holes into pure energy.

At 10²⁰ there is still a Universe of sorts, but the density is so small that, if you were put into it at a random point, you would be highly unlikely to see anything in your sky. But the Universe would still be out there, going about its business, expanding, it seems, at an ever-increasing rate. This is all so long after my 35th birthday that personally I am refusing to worry about it !

Cheers

Brian May

Will the Universe continue to expand indefinitely?

Phil - Northern Ireland

Currently, we believe that the Universe's expansion is accelerating (rather than slowing down under the influence of gravity), thanks to the mysterious 'dark energy'. As we don't understand this force at all, it's difficult to say what it will do in the future. Even if it turned off today, though, there is not enough stuff in the Universe to provide enough gravitational pull to reverse the expansion.

Chris Lintott

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