The term light year is often used by astronomers to express distances in space. At first read it sounds like a measure of time, but it’s actually a measure of distance. Space is so incredibly big that conventional measures, like the mile or kilometer, fall short of being useful. You just get so many zeros that the numbers become incomprehensible. For example, the distance to the nearest star, Alpha Centauri, is about 39,900,000,000,000 km, or 20,000,000,000,000 miles. All those zeros tend to impede comprehension.
One light year is the distance light will travel in one year. Light moves at the incredible speed of 186,000 miles/second. In one year, it will travel about six trillion miles! So we can use this huge unit of measurement to express the distance to Alpha Centauri as just 4.3 light years. Light from that star takes 4.3 years to reach Earth. Not only is this more concise, it also provides some insight into the space-time interval between there and here, and then and now. When you look at Alpha Centauri you are seeing it as it was 4.3 years ago. It’s taken that long for the light you see to get from there to here. For more distant objects like Sirius (see above) the time interval is even greater. When you look into space, you literally look back in time. |
Universe and Galaxies Quiz Part 2 Review
the_big_bang_theory.ppt | |
File Size: | 4517 kb |
File Type: | ppt |
What do we see when we look out into the universe?
Evidence for The Big Bang Model
First Piece of Evidence:
· the universe’s apparent expansion · the distance between galaxies and groups of galaxies seems to have been increasing with time · this is supported by redshifts in the spectra of galaxies, as studied by Edwin Hubble in 1929 · the redshifts show that distant galaxies in all directions are receding from Earth faster than nearby galaxies · because they are moving apart, they must have been closer together in the past |
Second Piece of Evidence:
· discovery of radiation apparently left over from the universe’s beginning · the radiation is called cosmic background radiation · although the redshift of this cosmic background radiation has moved beyond the visible part of the spectrum, infrared and radio telescopes can detect the radiation · the temperature of this radiation has been precisely measured · the temperature was found to be -270.3oC (similar to what the cosmologists – scientists who study the universe - had predicted, taking into account the amount of time that the universe has had to cool) · the background radiation varies very little across the sky |
The Known Universe--Zoom out into the universe all the way to the CMB
How Old?
Formation of the Elements in the Universe
Expansion Rate
Over the decades, that rate of expansion – called the Hubble Constant – has been measured many different ways. Using Cepheid variables is still a foundation of the work, though, and a new study just released by astronomers using the Spitzer Space Telescope show that the rate of expansion is 74.3 +/- 2.1 kilometers per second per megaparsec.
What this means is that a galaxy one megaparsec away (that is, 3.26 million light years) will be moving away from us at 74.3 km/sec. If you double the distance to 2 mega parsecs, a galaxy would be moving away at twice that speed, or 148.6 km/sec. |
The expansion of the universe. Play with Hubble’s lawWhat is the universe expanding into?
|
The Formation of the Universe |
Death of the Universe
|
|
|
How Big is the Universe?
|
Where was the big bang?
|
What is the universe?
|
Why is the sky dark?
|
|
|
|
Our Universe as an image (actually only 0.000001% of it)
Olber's Paradox--Why is the sky dark?
Try out this interactive website that investigates why is the sky dark at night? Olbers’ Paradox
Dark Matter--As much as we know so far. This stuff is a great mystery.
Parallel Universes?
|
|
Universal address?
Cosmic Microwave Background Radiation
Credit to Jon Kaufman and Jorge Cham at PHD Comics. http://phdcomics.com/comics.php
|
Time in the Universe
by mayra.artes.
Explore more infographics like this one on the web's largest information design community - Visually.
Explore more infographics like this one on the web's largest information design community - Visually.
Assorted Universe Links
• Welcome to the Universe Videos:
I – Introduction; II – Beyond the Sky; III – The Size of Things
• Videos on the Size of the Universe:
* American Museum of Natural History - The Known Universe
* Star Size Comparison
* What is the Size of the Universe?
* Size of the Universe
* Journey To The Edge Of The Universe
* From Nothing to Everything: How the Universe Works
• Khan Academy Videos:
- Scale of the Large and Scale of the Small
- Scale of the Earth and Sun – as well as videos on the scale of the universe, the nearest stars, and the galaxy
- Big Bang and the Expansion of the Universe
• Welcome to the Universe Videos:
I – Introduction; II – Beyond the Sky; III – The Size of Things
• Videos on the Size of the Universe:
* American Museum of Natural History - The Known Universe
* Star Size Comparison
* What is the Size of the Universe?
* Size of the Universe
* Journey To The Edge Of The Universe
* From Nothing to Everything: How the Universe Works
• Khan Academy Videos:
- Scale of the Large and Scale of the Small
- Scale of the Earth and Sun – as well as videos on the scale of the universe, the nearest stars, and the galaxy
- Big Bang and the Expansion of the Universe