The first in a series of briefings answering the most relevant, debatable, and interesting questions in astronomy.
Why is space black?
With billions of stars and galaxies shining, you would have thought the sky will be shining bright, however as you have seen from spae photos such as the one above, it is all black. One reason might be that as objects get further and further starlight gets dimmer and dimmer. With the exponential expansion of the universe, light coming from stars and galaxies will take more time to reach our eyes, hence limiting light’s reach across the universe. In the distant future, the universe would be so expanded there will be no light at all because of the distance, ending up in a pitch dark empty space. The other explanation might be due to the vacuum of space, with almost no particles for light to scatter on, it directly reaches our eyes as black.
What do people mean when they say observing into space is looking at the universe's past?
Light travels at nearly 300 million meters per second, since it takes 1.3 seconds for light on the moon to travel to Earth, we are actually seeing the moon 1.3 seconds ago. Light from the sun takes 8 minutes to travel back to Earth, so if the sun suddenly vanishes, we need to wait 8 minutes to start feeling the effects on Earth. Light years, a unit of distance, uses the distance light travels in a year as a method of measurement. Proxima Centauri is 4.2 light-years away, so when an astronomer points their telescope in the direction of the star, they are seeing it from 4 years ago. But when scientists observe the depths of space, they need to take into account the expansion of the universe.
Why do rockets have stages?
It is about fuel, if you want to shoot a one-stage rocket into space, you will need tremendous amounts of fuel. Setting up the rocket in stages enables the rocket to detach a stage when all of its fuel is used up. That reduces the weight of the rocket and allows less fuel for the rest of the rocket.
Why is Mars red?
The surface of Mars is covered with iron oxide, the same compound that gives iron rust its hue. But the reason behind the color is still a mystery. Experts are sure that this process happened due to weathering, some scientists hypothesize it is affected by the oxygen coming from water molecules or other molecules in the atmosphere, others think oxidation happens gradually over billions of years, as sunlight broke down carbon dioxide and other molecules in the atmosphere, producing oxidants such as hydrogen peroxide and ozone. Certain astronomers are pushing the theory that Martian dust storms rusted the iron and exposed the oxygen-rich parts, in the end, scientists still do not have a consensus and more research needs to be done.
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