How can a space instrument measure such a faint difference?
The polarizing Michelson interferometer measured differences. An external calibrator filled the sky aperture during calibration, and sensitive bolometers recorded the interferogram.
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OBSERVATION & MODEL
Read the cosmic background spectrum
These are published observations after calibration and foreground modeling. NASA’s intensity column combines a 2.725 K reference blackbody with measured residuals. Moving temperature changes only the comparison model.
The intensity scale is fixed. The small uncertainties become visible in the residual plot below.
The differences reveal more than the peak
The vertical range adapts to the current and saved comparisons. Error bars describe the archived bins, which are correlated.
RMS summarizes the displayed reference-relative differences. It is not a fit probability or a temperature confidence interval: neighboring bins are correlated, and the archive already uses a fitted reference.
- Archived intensity
- 383.478 MJy/sr
- Archived residual
- -10 kJy/sr = -0.01 MJy/sr
- Pointwise uncertainty
- ±18 kJy/sr (1σ)
- Current reference-relative difference
- -0.010000 MJy/sr
How the comparison is constructed
r(T) = r_archive + Bν(2.725 K) − Bν(T)
Residuals and errors in the source table are kJy/sr; divide by 1000 for MJy/sr. We preserve the archived residual exactly at 2.725 K. Recalculating the original baseline with modern SI constants at the printed wavenumbers differs by up to 0.007598 MJy/sr, so this is explicitly a reference-relative comparison.
Bν = (2hν³/c²) / [exp(hν/kT) − 1], with ν = 100cw for w in cm⁻¹. The galaxy template is not subtracted again. The later published 2.72548 K temperature combines other evidence and is not a value this table independently recovers.
Read all 43 original rows and comparison values
| cm⁻¹ | Intensity MJy/sr | Residual kJy/sr | 1σ kJy/sr | Galaxy model kJy/sr | Current difference MJy/sr |
|---|---|---|---|---|---|
| 2.27 | 200.723 | 5 | 14 | 4 | 0.005000 |
| 2.72 | 249.508 | 9 | 19 | 3 | 0.009000 |
| 3.18 | 293.024 | 15 | 25 | -1 | 0.015000 |
| 3.63 | 327.77 | 4 | 23 | -1 | 0.004000 |
| 4.08 | 354.081 | 19 | 22 | 3 | 0.019000 |
| 4.54 | 372.079 | -30 | 21 | 6 | -0.030000 |
| 4.99 | 381.493 | -30 | 18 | 8 | -0.030000 |
| 5.45 | 383.478 | -10 | 18 | 8 | -0.010000 |
| 5.9 | 378.901 | 32 | 16 | 10 | 0.032000 |
| 6.35 | 368.833 | 4 | 14 | 10 | 0.004000 |
| 6.81 | 354.063 | -2 | 13 | 12 | -0.002000 |
| 7.26 | 336.278 | 13 | 12 | 20 | 0.013000 |
| 7.71 | 316.076 | -22 | 11 | 25 | -0.022000 |
| 8.17 | 293.924 | 8 | 10 | 30 | 0.008000 |
| 8.62 | 271.432 | 8 | 11 | 36 | 0.008000 |
| 9.08 | 248.239 | -21 | 12 | 41 | -0.021000 |
| 9.53 | 225.94 | 9 | 14 | 46 | 0.009000 |
| 9.98 | 204.327 | 12 | 16 | 57 | 0.012000 |
| 10.44 | 183.262 | 11 | 18 | 65 | 0.011000 |
| 10.89 | 163.83 | -29 | 22 | 73 | -0.029000 |
| 11.34 | 145.75 | -46 | 22 | 93 | -0.046000 |
| 11.8 | 128.835 | 58 | 23 | 98 | 0.058000 |
| 12.25 | 113.568 | 6 | 23 | 105 | 0.006000 |
| 12.71 | 99.451 | -6 | 23 | 121 | -0.006000 |
| 13.16 | 87.036 | 6 | 22 | 135 | 0.006000 |
| 13.61 | 75.876 | -17 | 21 | 147 | -0.017000 |
| 14.07 | 65.766 | 6 | 20 | 160 | 0.006000 |
| 14.52 | 57.008 | 26 | 19 | 178 | 0.026000 |
| 14.97 | 49.223 | -12 | 19 | 199 | -0.012000 |
| 15.43 | 42.267 | -19 | 19 | 221 | -0.019000 |
| 15.88 | 36.352 | 8 | 21 | 227 | 0.008000 |
| 16.34 | 31.062 | 7 | 23 | 250 | 0.007000 |
| 16.79 | 26.58 | 14 | 26 | 275 | 0.014000 |
| 17.24 | 22.644 | -33 | 28 | 295 | -0.033000 |
| 17.7 | 19.255 | 6 | 30 | 312 | 0.006000 |
| 18.15 | 16.391 | 26 | 32 | 336 | 0.026000 |
| 18.61 | 13.811 | -26 | 33 | 363 | -0.026000 |
| 19.06 | 11.716 | -6 | 35 | 405 | -0.006000 |
| 19.51 | 9.921 | 8 | 41 | 421 | 0.008000 |
| 19.97 | 8.364 | 26 | 55 | 435 | 0.026000 |
| 20.42 | 7.087 | 57 | 88 | 477 | 0.057000 |
| 20.87 | 5.801 | -116 | 155 | 519 | -0.116000 |
| 21.33 | 4.523 | -432 | 282 | 573 | -0.432000 |
Data provenance
Every non-comment row from NASA’s released table, in original order. No points were added or removed. The download page dates delivery to March 2003; the file header dates its initial revision to May 2005. Both are preserved in our source record.
SHA-256: df793c3dca09ebfa7dbc5aa0ec1951daa8884431bc30eff28a710d7516cf50fa
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MAKE THE CONNECTION
Which evidence makes the brightness scale traceable?
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HISTORY THROUGH EVIDENCE
Read all 43 published points
The archive provides 43 wavenumbers, a reconstructed intensity, measured residuals, uncertainties and a Galactic model column.
Explore how the evidence changed the explanation →