The Allen Telescope Array is potentially capable of detecting a strong radio signal from Proxima b, or any other star system with strong enough radio transmissions. It has successfully worked in concert with other radio telescopes across extremely long baselines to resolve the event horizon of a black hole: arguably its crowning achievement. (WIKIMEDIA COMMONS / COLBY GUTIERREZ-KRAYBILL)

Ask Ethan: How Does The Event Horizon Telescope Act Like One Giant Mirror?

It’s made up of scores of telescopes at many different sites across the world. But it acts like one giant telescope. Here’s how.

If you want to observe the Universe more deeply and at higher resolution than ever before, there’s one tactic that everyone agrees is ideal: build as big a telescope as possible. But the highest resolution image we’ve ever constructed in astronomy doesn’t come from the biggest telescope, but rather from an enormous array of modestly-sized telescopes: the Event Horizon Telescope. How is that possible? That’s what our Ask Ethan questioner for this week, Dieter, wants to know, stating:

I’m having difficulty understanding why the EHT array is considered as ONE telescope (which has the diameter of the earth).
When you consider the EHT as ONE radio telescope, I do understand that the angular resolution is very high due to the wavelength of the incoming signal and earth’s diameter. I also understand that time syncing is critical.
But it would help very much to explain why the diameter of the EHT is considered as ONE telescope, considering there are about 10 individual telescopes in the array.