I was just reading a discussion on Instagram (a mistake) which said that if gravity was a bit stronger the universe would collapse (yes) or a bit weaker it would expand and fly apart forever (again yes). It then goes on to say, since gravity is so precise God MUST exist! I took umbridge at this I said :
Huh? There were possibly other universes that collapsed or expanded.. We are just lucky to be in this one. Its not precision its just that we are able to observe it. Its like saying I’m five foot three tall, therefore my short trousers fit!
In any case the Universe IS expanding, There is a considerable red shift and we can see Galaxies are moving apart. There is no sign that its slowing down… Has God forgotten and left the Universe on too low a gravity? I know – I’m cynical.
I like knowing things, so I thought I would look u some measurements.
The shortest distance on earth I could find was the thinnest section of the crust of the Earth which is only under the deep oceans and is mainly made up of iron bearing rock. That is about 5km.
But the thickness of the Earth’s crust varies between 5km and 70km, so the average would be about 35 kilometers. To give you an idea of how far that is, it’s approximately the same as Dover to Calais, which is 33.3km.
The distance from the Earth’s surface to space is 100 kilometers. Or three times the distance from Dover to Calais.
Going up in size, the distance from the Earth’s surface to the centre of the Earth is 6,371km. Which is 63 times the distance to space.
Now we go a bit further. The escape velocity from Earth is 11.19 kilometers per second. That is the slowest speed something would have to move to fly up into space and leave Earth’s gravity for good. The more massive the object, the more effort it would take to leave the gravity well of an object. So a gas giant planet is huge compared with the Earth but is less dense on average. I don’t know the figures. I didn’t look them up, but I read that if we were as big as Saturn it could gloat on our sea?
Going further out, the Moon, which is the furthest human beings have travelled to after reaching escape velocity is 384,400km away.
If you want to travel to the Sun the distance is 150,800,000 kilometers….
But man-made objects have gone further. We have sent probes into the vastness of space. Voyager Two has left the Solar system and is currently about 18,603,199,501 kilometers away. In distance at the speed of light that’s 17 hrs 14 minutes and 13.5 seconds (approximately) as of yesterday.
Of ccourse that’s nothing compared with the nearest star to our Sun. Which is about 4 light years away from the Solar system. And then… Space is infinite…
A few years ago I did this digital drawing of the whirlpool galaxy. This was done at a website called sketchfu. I’ve written about it before.
When you think of how many billions and trillions of stars there are in a galaxy, and how many millions or billions, or many more, galaxies there are in the universe. It is awe inspiring. Looking out across space is looking back in time. The visible stars light, and the light from distant galaxies, has been travelling towards us for great lengths of time. Even the light from the Sun takes eight minutes to travel to the Earth. Is it that we are ahead in time compared to the rest of the universe? Or maybe not? Maybe we are behind? Because if something happened on another world or star, we would not find out till their light reached us, by which time that occurance would be possibly billions of years in their past.
Time, intriguing, confusing, we can only travel with it. Gravity can distort it, lengthen it. So much to know… So much to find out.
Watching a programme about gravity and quantum physics. The very big and the very small…
Hard to follow. There is apparently a fundamental problem in our understanding of the universe. General relativity explains Stars and galaxies. Quantum mechanics explains Atoms. But when you get to black holes the laws of nature fail.
Today Nasa published the very first image of a real black hole. Before today any images were just illustrations or mock ups.
The singularity at the centre of a black hole is apparently the same sort of thing as the singularity at the beginning of the universe.
The programme shows how something called quantum gravity explains the universe. Now we have seen a real black hole they may be able to take the theories further.
It does! I started writing this over 12 hours ago but then the battery on my tablet went flat so I had to wait until now .
Anyway, time does tick by, sometimes I know exactly when the alarm is going to go off, and it does. I can wake up a second before the alarm clock goes off….nothing is clicking or whirring or spinning to give me a cue or a clue. Same with the alarm on our oven, last night I got up from my chair to check it just before it went off.
One explanation is the brain has tiny cells beating regularly giving us a sense of time. There are also electric nodes in your heart that regulate your heartbeat, and your breathing is a regular rhythm allowing you to get just the right amount of air.
But what is time, why do we feel times arrow? Why does a cup fall and then break as it hits the floor? Why isn’t it on the floor then bouncing back up onto the table, reforming from smashed to solid in a second? There is something called entropy, everything breaks down over time. Everything tends towards chaos. The Universe is cooling, as space expands. Astrophysicists speak of the heat death of the universe as everything spreads out and cools towards absolute zero. Galaxies are flying away from each other. If things continue, in many billions or trillions of years, we would have completely black skies, no stars in sight. Our Sun will have cooled to a husk of burnt matter and all the other Stars will fly off away for us. There is something called red shift, as galaxies move away their light shifts towards the red end of the spectrum, the larger the red shift the faster they are moving. There are theories about things called dark energy and dark matter that try to explain this, but I wouldn’t know where to start with that aspect of space time.
Time ticks for everything, although time may not actually exist, it might just be our way of measuring the passing of things happening, but not understanding the universe. But if it is real there may be an advantage of time. The end of the universe or more likely its continuous, infinite existence, will not happen in our time. But a long long long time in the future.