Asked Questions
1: Can you see satellites and the space station, etc from the ground with the unaided eye?
3: What is UTC?
Q: Can you see satellites and the space station, etc from the ground with the unaided eye?
A: Yes you can! A great site for satellite predictions is Heavens-Above. Or you can just go outside and look at the sky shortly (a few hours) after sunset or before sunrise to look. They will look just like stars but satellites will slowly track across the sky (normally takes around 5-8 minutes) usually from west to east, much slower moving then a meteor and a more white-yellow colour.
Q: Is it true that we can look back in time because light from the beginning of the universe is only now beginning to reach us?
A: Yes it is true. When you hear an aircraft go overhead, the sound always seems behind it, that's because the sound waves take a while to reach your ear (sound waves travel at only 1 240 kilometres/hour), so you are hearing the aircraft as it was a few seconds earlier.
Light from the Sun takes 8 minutes to reach the Earth (travelling at 300 000 kilometres/second), so when you look up you are seeing it as it appeared 8 minutes ago. With a star that is 10 light-years away, the light waves from the star have taken 10 years to reach us, so we see the star as it was 10 years ago.
If you were on another planet orbiting a star 65 million light-years from Earth and had a powerful enough telescope, you could see dinosours walking around on Earth, and see what caused their extinction. This is because the light from Earth has taken 65 million years to reach you, and as a result your 65 million years behind in your study of Earth history. And would have to wait another 65 million years just to see us as we are today.
A small point with the question, we can look back in time, but we don't have any choice about it, as we have to wait for the light to reach us, just the same as we can hear back in time because we have to wait for the sound to reach us from the aircraft, or whatever is making the sound.
A: UTC or Coordinated Universal Time. Uses the International Atomic Time, so one second of UTC is exactly the same as given by the atomic clocks. However due to varitaions in the Earth's rotation and orbit, a second must be added or deleted, known as a leap second, at the end of December, June, March or September, as necessary. To keep it in time with UT (Universal Time). UT and UTC are based on GMT (Greenwich Mean Time), which was renamed in 1928 to UT for scientific perposes. Basically UT, UTC and GMT are all the same time (to within 0.9 seconds at most).
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