Sunset

Only 93 million miles away. The sun sets… But it really set 8 minutes earlier! It’s just that light takes that long to get from the sun to us.

OK, now look up at the stars. Some of them are actual stars and others are nebulae and galaxies.

Light takes time to travel. They talk about light years, some stars are only a few light years away. Some are thousands, or millions, or billions of light years away.

Now think about radio waves. They travel at the speed of light too… So TV and radio signals from Earth started travelling from when we first broadcast radio back in the 1920’s or 30’s? Thats a sphere around the Earth with a radius of about 90 or 100 years. So a planet 90 light years away might just about be hearing our signals. Imagine what they would do. They can’t travel here at the speed of light, but they might reply, but that will take 90 years to reply. Closer stars could have planets that reply sooner. But it’s still going to be a boring conversation!

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