Philip Plait
Light
from the edge of the Sun’s face takes over 2 seconds longer to reach us than
from the middle.
Our Sun is big. Very, very big. How big? Think of it this way:
We see the Sun as a disk in the sky. Of course, it's actually a sphere, and we see the hemisphere facing us. That means the center of the Sun's face is closer to us than the edge, because it sticks out toward us. The difference in distance from the Earth to the center of the Sun's face, versus the distance from the Earth to the edge, is pretty much equal to the radius of the Sun: about 700,000 kilometers (430,000 miles).
A beam of light, the fastest thing in the Universe, moves at 300,000 kilometers per second. That means that light from the edge of the Sun takes a little over two seconds longer to reach us than light emitted from the center of the Sun's face!
In other words, when you look at the face of the Sun (and don't do so without adequate protection) you're not seeing all of it at the same time. _You're seeing the edge of it two seconds in the past compared to the middle_.
That's how huge the Sun is.
Our Sun is big. Very, very big. How big? Think of it this way:
We see the Sun as a disk in the sky. Of course, it's actually a sphere, and we see the hemisphere facing us. That means the center of the Sun's face is closer to us than the edge, because it sticks out toward us. The difference in distance from the Earth to the center of the Sun's face, versus the distance from the Earth to the edge, is pretty much equal to the radius of the Sun: about 700,000 kilometers (430,000 miles).
A beam of light, the fastest thing in the Universe, moves at 300,000 kilometers per second. That means that light from the edge of the Sun takes a little over two seconds longer to reach us than light emitted from the center of the Sun's face!
In other words, when you look at the face of the Sun (and don't do so without adequate protection) you're not seeing all of it at the same time. _You're seeing the edge of it two seconds in the past compared to the middle_.
That's how huge the Sun is.
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