Srila Prabhupada - "Whatever we see is within this one universe, we cannot see outside of it".

What we see in the material universe is all within our 4 billion mile diameter universe.

We CANNOT see outside our individual universe according to Srila Prabhupada.

It is impossible to see the millions of other Brahmandas outside our inner universe (that s deep inside a massive Brahmanda) because of being surrounded by 7 thick material layers, Srila Prabhupada explains-

Srila Prabhupada - ''The Vedic literature informs us that within this universe there is one sun, which is moving. The Western theory that all the luminaries in the sky are different suns is not confirmed in the Vedic literature.

Nor can we assume that these luminaries are the suns of other universes, for each universe is covered by various layers of material elements, and therefore although the universes are clustered together, we CANNOT see from one universe to another.

In other words, whatever we see is within this one universe.

In each universe there is one Lord Brahmā, and there are other demigods on other planets, but there is only one sun''.

 - Srimad Bhagavatam Canto 5 Chapter 21 Text 11, Purport:

Maybe the material scientists are tricked by the "hall of mirrors" effect that some other scientists have suggested is caused reflections of light from other luminaries that makes the our small material universe appear to be way bigger than what it is.