The Holy City in Light Cone

Light cone, made up of future light cone and past light cone, is the New Jerusalem (the Holy of Holies) in the form of a glowing Sandglass (Hourglass). The future light cone is the upper bulb of the Sandglass, the past light cone is the lower bulb, and the sand particles are photons or twinkling stars.
The city was pure gold, like unto clear glass (Revelation 21:18) "KJV"
The city: the New Jerusalem
The city was pure gold: the city is sparkling with the golden colour of light
Glass: Sandglass

Light cone is the giant black hole formed when two black holes are merged or reconciled. The first black hole is the base of the past light cone, and the second black hole is the base of the future light cone.

The base of each black hole is the 'ring of light' known as halo or glory. The two black holes are two glories whose sum is equal to the glory of God.

Since light cone is the product of the sum of two black holes, the light cone is the light called the glory of God.

The New Jerusalem is at the level of Gravitational Wave Astronomy where a new light cone is formed every time two black holes are reconciled to form a single black hole.

Each day is a light cone where the two glories are the circle of night and day respectively. The glory representing the twelve hours of the night is a lunar halo, the glory representing the twelve hours of the day is a solar halo, and the light cone is the sum of the two glories.

Therefore, day and night are two black holes, and every twenty four hours (everyday) is a giant black hole made up of two black holes.

Consequently, everyday is a glowing Sandglass (an Hourglass) and photons are the grains of sand. A day is a supermassive black hole, and photons are the twinkling stars inside the black hole.
The street of the city was pure gold, like transparent glass. (Revelation 21:21) "NKJV"
The street of the city was pure gold: the golden colour of light.

As it were a transparent glass: the day is as bright as a transparent hour glass

Everyday is a light cone, and there are 365 light cones in a year and 366 light cones in a leap year.